How are Terracotta and Clay different? Clay is a raw material, but terracotta is clay that has been molded and fired. Terracotta items are often composed of any kind of organic clay, but earthenware clay has the brown-orange hue associated with the term. Low-temperature firing produces a porous and permeable surface in terracotta items.
What Is The Difference Between Clay And Terracotta?
Clay comes in a variety of colors, from white to grey to brown to deep red or orange, whereas terracotta has a unique red and orange tint. Clay is a natural substance containing hydro-aluminum silicate fine particulate matter and other minerals. Terracotta refers to a form of earthenware clay that is easily accessible and which has rich red and orange shades, pottery, or other articles produced with that clay.
What is Clay?
Clay may have varied colors depending on the soil composition, from white to gray to brown, or orange, and the red-orange color of terracotta. The term clay is a generic phrase used to mean materials for three-dimensional object modeling and creation.
Clay can consist of natural components such as minerals, however, varieties of clay can also be constructed of man-made materials such as polymers. The most common varieties of organic clay are earthenware, stoneware, and kaolin.
There are variable degrees of plasticity in different clay formations. The capacity to stretch or bend is called plasticity. The more plastic a clay, the simpler it is to mold in many forms, i.e. Tone may change in colors from white to gray to brown to deep red or orange depending on the soil composition.
Various kinds of clay with various characteristics are available. Depending on their characteristics, they have varied purposes. The three common types of pottery are Earthenware, Stoneware, and Porcelain.
Earthenware Clay
Earthenware clay includes iron and other impurities, which allow optimal hardness to be achieved at low temperatures. It’s permeable, extremely plastic, and easy to use. Earthenware is usually formed on a pottery wheel then fired in a kiln to turn it into a glazed ceramic.
Earthenware pots made from clay fired at low temperatures are porous and require heavy layers of glazing to be utilized for water storage. Earthenware clay pots are frequently produced from impure clays that contain rock and sand particles. Clay for earthenware pots is frequently collected from streams where it has settled and produced clay deposits. Temperatures of 1700 to 2100 degrees Fahrenheit are used to burn earthenware clay pots.
Stoneware Clay
Stoneware clay is generally grayish in its raw form. Usually, it is burned at high temperatures, changing its color to medium gray or brown. The clay is hard, thick, and stone-like after the burning. It is permeable and flexible.
Stoneware is a kind of clay that is fired between 2100 and 2300 degrees Fahrenheit at a medium temperature. Stoneware is the most common form of clay used to make tableware and cookware. Stoneware is constructed of strong, durable clay with few impurities, making it less porous than earthenware and hence suitable for storing liquids without leaking.
Porcelain Clay
Porcelain clay is a versatile clay that can make beautiful and fine art home products. Porcelain is burned at a much greater temperature than other clays (up to 2550 degrees Fahrenheit). The material becomes vitrified as a result of the firing. Stoneware is used to make tableware and is fired at temperatures ranging from 2100 to 2300 degrees Fahrenheit.
Another form of clay is porcelain, which is produced largely of pure kaolin or China clay. Porcelain clay has relatively few impurities and hardens at extremely high temperatures. Porcelain is a tough clay that may be easily shattered. The surface of porcelain becomes smooth and glossy after firing, thus reducing the need for glazing.
Clay pots can also be classified by the type of clay used to manufacture them. The distinction between purity and color is straightforward. Porcelain is a form of clay that is approximately 100 percent pure and is used to create high-end china and pots. Red, white, yellow, gray, and black clays can also be used to make pots.
What is Terracotta?
Terracotta (Latin terra cotta, terra-cotta pots) is an Italian word meaning ‘baked earth.’ Terracotta means baked earth in Italian. Terracotta is a low fire iron rich porous reddish fired products made in Italy Terracotta refers to the pottery formed of organic clay that is glazed or unglazed inside the kiln of a potter. Archeologists and historical artists refer to artifacts produced without the wheel of a potter as terracotta, such as sculpture or tile. The potter’s objects are known as pottery. Terracotta is also the fired clay color, which contains a significant quantity of iron oxide.
Terracotta may refer to a kind of clay with deep red and orange colors that is easily accessible in which many items made using. Terracotta also refers to pottery and other organic clay products that are baked in a kiln. Some people also characterize any clay product with a reddish-orange tint by using the word terracotta. Terracotta pots are generally dark red, low fire red or yellowish-brown in color, whereas clay pots come in a variety of hues. Clay pots and pottery might be white, black, blue, green, or any other hue, but terracotta is always vivid red. The main difference between clay and terra cotta is color. Clay has a wider spectrum of colors than terracotta. In my opinion this make a big difference between the two clays.
Terracotta clay is a reddish-orange clay that may be found almost anywhere. This color comes from the iron component, which interacts with air to produce various colors such as orange, red, yellow, and even pink. Terracotta is not, therefore, pure clay. Furthermore, terracotta is a porous clay that is easy to deal with. It comes in two varieties: glazed and unglazed. It may also be made waterproof with one layer of glaze. Most notably, terracotta is an earthenware material.
A big advantage of Terracotta especially for potted pants is that Terracotta is very porous. The porosity comes into play due to the fact the earth-based medium allows air in to circulate within a pot. The air movement stimulates root growth and promotes healthy plants which in my opinion is a big advantage for potting plants in Terracotta. Now you know why you see so many Terracotta pots, right?
Earthenware artwork, clay containers, water, and wastewater pipes, roofing tiles, and bricks are all examples of terracotta. Terracotta is either clay-based unglazed or glazed but regardless it very porous after firing. It has a lengthy and illustrious history all throughout the world.
Clay Versus Terracotta Summary
Terracotta is clay that has been molded and fired. Low-temperature firing produces a porous and permeable surface in terracotta items. Terracotta items are composed of any kind of organic clay, but earthenware clay has the brown-orange hue associated with the term.
Ceramic Firing Techniques – Firing is the method for making ceramics that can endure a lot of pressure. Firing takes place in an oxygen-rich environment. When it comes to firing pottery, there are two primary methods. The use of kilns and open firing are the two methods. The crucial step in the ceramic process is firing. It’s the point at which clay transforms from clay to usable ceramic.
Clay is a natural substance containing hydro-aluminum silicate fine particulate matter and other minerals. Terracotta refers to a form of earthenware clay that has rich red and orange shades. Clay comes in a variety of colors, from white to grey to brown to deep red or orange.
Comparison of Key Differences Between Clay And Terracotta
Clay Characteristics
1. Clay Composition
Contains particles of hydrous aluminum silicates and other materials.
2. Clay Color
Has many colors ranging from Gray, Brown to Deep Red and Orange.
3. Clay Forms
Available in many different forms like earthenware, stoneware, and porcelain.
Terracotta Characteristics
1. Terracotta Composition
An earthen clay is abundantly available and easily accessible with a heavy iron component. A very porous clay. Terracotta safe for food. did you know Martha Stewart bakes with terracotta? Manufacturers of pottery do not use lead in their clay however, even if trace levels of lead are present, it will not seep into your food unless it is very acidic, such as citrus.
Terracotta tiles made of clay. A non-combustible alternative is terracotta clay tile. For Southwestern, or Spanish-style buildings, it’s a common choice. However, it does require some care for good fire protection, I’m particularly talking about the barrel-shaped tiles. This is due to gaps between the under-layment and the tile sheathing might occur.
2. Terracotta Color
Rich Red-Orange color emanating from the high iron content.
3. Terracotta Form
Mainly earthenware that cones in glazed or unglazed forms.
Definitions
Groggy Clay
Grog is ground-up clay that has been fired. Grog is available in a variety of particle sizes, ranging from fine to coarse. It’s used to keep clay bodies from shrinking. Grog in a clay body minimizes shrinkage and makes it less likely for a piece to shatter during drying and fire while hand-building.
Grog, commonly known as firesand or chamotte, is a ceramics raw material. It contains a lot of silica and alumina. It’s usually sold as a powder or chippings, and it’s a key component of Coade stone.
Grog is made up of 40 percent alumina, 30 percent silica, 4 percent maximum iron(III) oxide, and up to 2% calcium oxide and magnesium oxide combined.
It has a melting point of around 1,780 °C (3,240 °F). It has a boiling point of over 9,000 degrees Celsius (16,230 degrees Fahrenheit). Its maximal water absorption rate is 7%. Thermal conductivity is 0.8 W/(mK) at 100 °C and 1.0 W/(mK) at 1000 °C, with a thermal expansion coefficient of 5.2 mm/m.
Grog is used to give pottery and sculpture a gritty, rustic feel known as “tooth,” as well as to prevent shrinkage and facilitate uniform drying. Cracking, crows feet patterning, and lamination are all prevented as a result of this. The coarse particles allow gases to escape by opening the green clay body. During shaping, grog improves structural strength to hand-built and thrown pottery, but it might reduce fired strength.
The tighter the clay bonds, the denser and stronger the burnt product. In the dry condition, the strength of grog down to the fineness of that passing through a 100-mesh sieve rises, but it decreases with material passing through a 200-mesh screen.
Qin Shi Huang Emperor of China – Terracotta Soldier
One of the Terracotta Army’s warriors (Terracotta Soldier), mold-made Ancient Chinese terracotta statues of Qin Shi Huang’s army, the first Emperor of China. Qin Shi Huang was the first emperor of a united China and the founder of the Qin dynasty. He was Zheng, King of Qin, from 247 to 221 BC. After the Qin destroyed all of the other Warring States and united all of China in 221 BC, he became China’s first emperor at the age of 38.
Non-firing Clay
No Fire Clay (also known as Sunclay or self-hardening clay) is a non-toxic, soft and malleable modelling clay that air dries. It’s not to be confused with Kaolin clay, baked clay, ball clay, modeling clay or polymer clay. It is manufactured from natural components and may be manipulated with water and tools much like genuine clay. The No Fire Clay, like clay, must be manipulated with water to keep it wet. Self-hardening clay, also known as air-dried or non-firing clay, is a direct modeling medium that cures naturally without the need for mold creation or casting.
Bone China
Bone china is a porcelain kind made from bone ash, feldspathic material, and kaolin. It is described as “clear ware with a transparent body” that contains at least 30% phosphate generated from animal bone and calculated calcium phosphate. Bone china is the most durable of the porcelain or china ceramics, with extremely high mechanical and physical strength as well as chip resistance. It is also recognized for its high levels of whiteness and transparency. Because of its great strength, it may be made with narrower cross-sections than other porcelains. It’s vitrified like stoneware, but the mineral characteristics make it transparent.
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References
Dahiya, S., Siwach, P., Panghal, A., & Sindhu, S. (2021). 11 Terracotta Pottery Catastrophe. Entrepreneurship and Big Data: The Digital Revolution, 153. https://books.google.com/books?hl=en&lr=&id=Atk9EAAAQBAJ&oi=fnd&pg=PA153&dq=Terracotta+pottery&ots=8jQ5kA1SeK&sig=RMT_pO4EyOiQ9PlelaXRAz2DXbc#v=onepage&q=Terracotta%20pottery&f=false
Mishra, S. P., & Mansuri, A. J. (2016). Problems of Indian red clay pottery (Terracotta) industries and policies for development. International Journal of Advanced Research in Management and Social Sciences, 5(11), 12-29. https://garph.co.uk/IJARMSS/Nov2016/2.pdf
Mazzocchin, G. A., Agnoli, F., & Colpo, I. (2003). Investigation of roman age pigments found on pottery fragments. Analytica Chimica Acta, 478(1), 147-161. sciencedirect.com/science/article/abs/pii/S0003267002014769
